docs: def set_or_create_content(self, page, language, ctype, body):
          """Set or create a :class:`Content <pages.models.Content>` for a
          particular page and language.
  
          :param page: the concerned page object.
          :param language: the wanted language.
          :param ctype: the content type.
          :param body: the content of the Content object.
          """
          try:
              content = self.filter(page=page, language=language,
                                    type=ctype).latest('creation_date')
              content.body = body
          except self.model.DoesNotExist:
              content = self.model(page=page, language=language, body=body,
                                   type=ctype)
          content.save()
          return content